Differential Regulation of the Human Cyp3a4 Promoter in Transgenic Mice and Rats

Zhang, Weisheng; Purchio, Anthony F.; Coffee, Richard; West, David B.

doi:10.1124/dmd.32.2.163

Cited by 10 publications

(6 citation statements)

References 16 publications

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“…However, lipids have been shown to interfere with the detection of cholesterol, proteins, and other biomolecules by ELISA. 45 − 47 Indeed, several studies have shown that lipids can obscure the detection of PrP Sc by ELISA in blood 32 , 48 and tissue homogenates. 49 …”

Section: Resultsmentioning

confidence: 99%

Mechanism of Scrapie Prion Precipitation with Phosphotungstate Anions

et al. 2015

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The phosphotungstate anion (PTA) is widely used to facilitate the precipitation of disease-causing prion protein (PrPSc) from infected tissue for applications in structural studies and diagnostic approaches. However, the mechanism of this precipitation is not understood. In order to elucidate the nature of the PTA interaction with PrPSc under physiological conditions, solutions of PTA were characterized by NMR spectroscopy at varying pH. At neutral pH, the parent [PW12O40]3– ion decomposes to give a lacunary [PW11O39]7– (PW11) complex and a single orthotungstate anion [WO4]2– (WO4). To measure the efficacy of each component of PTA, increasing concentrations of PW11, WO4, and mixtures thereof were used to precipitate PrPSc from brain homogenates of scrapie prion-infected mice. The amount of PrPSc isolated, quantified by ELISA and immunoblotting, revealed that both PW11 and WO4 contribute to PrPSc precipitation. Incubation with sarkosyl, PTA, or individual components of PTA resulted in separation of higher-density PrP aggregates from the neuronal lipid monosialotetrahexosylganglioside (GM1), as observed by sucrose gradient centrifugation. These experiments revealed that yield and purity of PrPSc were greater with polyoxometalates (POMs), which substantially supported the separation of lipids from PrPSc in the samples. Interaction of POMs and sarkosyl with brain homogenates promoted the formation of fibrillar PrPSc aggregates prior to centrifugation, likely through the separation of lipids like GM1 from PrPSc. We propose that this separation of lipids from PrP is a major factor governing the facile precipitation of PrPSc by PTA from tissue and might be optimized further for the detection of prions.

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Section: Resultsmentioning

confidence: 99%

Mechanism of Scrapie Prion Precipitation with Phosphotungstate Anions

et al. 2015

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“…Compared to the previously generated CYP3A4 -transgenic mouse models (Granvil et al, 2003; Robertson et al, 2003; Zhang et al, 2003; Zhang et al, 2004; Cheung et al, 2006), the major improvement in the current model was the inclusion of human PXR, the dominant activator of CYP3A4 transcription. All previous CYP3A4 mouse models were generated on a mouse PXR background, which does not mimic human CYP3A4 regulation because of the species differences in PXR in response to various ligands.…”

Section: Discussionmentioning

confidence: 99%

“…CYP3A4 -transgenic mouse models are valuable tools for studying the function and regulation of CYP3A4 in a whole animal system, and the functional significance of CYP3A4 expression can be evaluated under controlled conditions (Gonzalez and Yu, 2006). Previously, several CYP3A4 -transgenic mouse models were generated (Granvil et al, 2003; Robertson et al, 2003; Zhang et al, 2003; Zhang et al, 2004; Cheung et al, 2006). However, all of these mouse models are limited in transcriptional studies on CYP3A4 because of their mouse PXR background.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, dexamethasone and pregnenolone 16α-carbonitrile (PCN) activate rodent PXR but are weak activators of human PXR. Therefore the CYP3A4 -transgenic mouse models that have been generated are of limited utility for transcriptional and drug interaction studies because of their mouse PXR background (Granvil et al, 2003; Robertson et al, 2003; Zhang et al, 2003; Zhang et al, 2004; Cheung et al, 2006). The generation of double transgenic mice expressing human PXR and CYP3A4 would provide a solution to this problem.…”

Section: Introductionmentioning

confidence: 99%

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A Double Transgenic Mouse Model Expressing Human Pregnane X Receptor and Cytochrome P450 3A4

Ma¹,

Cheung²,

Krausz³

et al. 2008

Drug Metabolism and Disposition

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ABSTRACT:Cytochrome P450 3A4 (CYP3A4), the most abundant human cytochrome P450 in liver, participates in the metabolism of ϳ50% of clinically used drugs. The pregnane X receptor (PXR), a member of the nuclear receptor superfamily, is the major activator of CYP3A4 transcription. However, because of species differences in response to PXR ligands, it is problematic to use rodents to assess CYP3A4 regulation and function. The generation of double transgenic mice expressing human PXR and CYP3A4 (TgCYP3A4/hPXR) would provide a solution to this problem. In the current study, a TgCYP3A4/ hPXR mouse model was generated by bacterial artificial chromosome transgenesis in Pxr-null mice. In TgCYP3A4/hPXR mice, CYP3A4 was strongly induced by rifampicin, a human-specific PXR ligand, but not by pregnenolone 16␣-carbonitrile, a rodent-specific PXR ligand. Consistent with CYP3A expression, hepatic CYP3A activity increased ϳ5-fold in TgCYP3A4/hPXR mice pretreated with rifampicin. Most antihuman immunodeficiency virus protease inhibitors are CYP3A substrates and their interactions with rifamycins are a source of major concern in patients coinfected with human immunodeficiency virus and Mycobacterium tuberculosis. By using TgCYP3A4/hPXR mice, human PXR-CYP3A4-mediated rifampicin-protease inhibitor interactions were recapitulated, as the metabolic stability of amprenavir, nelfinavir, and saquinavir decreased 52, 53, and 99%, respectively, in the liver microsomes of TgCYP3A4/hPXR mice pretreated with rifampicin. In vivo, rifampicin pretreatment resulted in an ϳ80% decrease in the area under the serum amprenavir concentration-time curve in TgCYP3A4/ hPXR mice. These results suggest that the TgCYP3A4/hPXR mouse model could serve as a useful tool for studies on CYP3A4 transcription and function in vivo.

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“…Real-time in vivo biophotonic image analysis of mice expressing luciferase has been used to noninvasively characterize the response to drug treatments, disease progression, and other biological events [21–24] in transgenic mice. We found the RIP-luc transgene expression to be stable over time in adult mice during chow feeding and to increase during high-fat feeding as the mice gained weight.…”

Section: Introductionmentioning

confidence: 99%

In Vivo Monitoring of Pancreatic β-Cells in a Transgenic Mouse Model

Smith¹,

Zhang²,

Clermont³

et al. 2006

Mol Imaging

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We generated a transgenic mouse model (RIP-luc) for the in vivo monitoring of pancreatic islet mass and function in response to metabolic disease. Using the rat insulin promoter fused to firefly luciferase, and noninvasive technology to detect luciferase activity, we tracked changes in reporter signal during metabolic disease states and correlated the changes in luciferase signal with metabolic status of the mouse. Transgene expression was found to be specific to the pancreatic islets in this transgenic model. Basal transgene expression was tracked in male and female mice fed either a chow or a high-fat diet and in response to treatment with streptozotocin. Pancreatic bioluminescent signal increased in mice fed a high-fat diet compared with chow-fed animals. In a model of chemically induced diabetes, the bioluminescent signal decreased in accordance with the onset of diabetes and reduction of islet beta-cell number. Preliminary studies using islets transplanted from this transgenic model suggest that in vivo image analysis can also be used to monitor transplanted islet viability and survival in the host. This transgenic model is a useful tool for in vivo studies of pancreatic beta-cells and as a donor for islet transplantation studies.

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Differential Regulation of the Human Cyp3a4 Promoter in Transgenic Mice and Rats

Cited by 10 publications

References 16 publications

Mechanism of Scrapie Prion Precipitation with Phosphotungstate Anions

Mechanism of Scrapie Prion Precipitation with Phosphotungstate Anions

A Double Transgenic Mouse Model Expressing Human Pregnane X Receptor and Cytochrome P450 3A4

In Vivo Monitoring of Pancreatic β-Cells in a Transgenic Mouse Model

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